Definition: A data source is any system, file, feed or service that supplies data into another system, such as a data warehouse. Bringing in a new data source usually means understanding its structure, meaning and quality, and how it relates to existing data.
So what? Each new data source brings new risks: mismatched formats, duplicates, gaps and conflicting definitions. Understanding a source early helps testers focus on where it overlaps or clashes with existing data.
Examples: Adding an online retailer's customer and payment feed to an existing warehouse. Comparing a travel company's customer data against an existing customer profile.
